The Testimonies is a minor collection of five passages attributed to the Roman historian Dio Cassius of Nicaea. It is not enumerated among his principal works and likely represents a fragmentary compilation, possibly consisting of source material or excerpts drawn from his more substantial but now lost writings. Dio Cassius is chiefly renowned for his monumental 80-book Roman History, a comprehensive narrative spanning from Rome's mythical origins to the early third century CE. The specific thematic content of the Testimonies is not recorded, but given the scope of Dio's major historical project, it may have touched upon his characteristic interests in political analysis of imperial power, military campaigns, provincial administration, and the biographical treatment of emperors. The precise transmission of this collection is obscure; it likely survives, as with many fragments of Dio's larger history, only through preservation within later Byzantine excerpting traditions, such as those of John Xiphilinus and John Zonaras. While the Testimonies itself possesses no documented independent influence, the broader historical corpus of Dio Cassius was fundamental to Byzantine chroniclers and remains a standard source on the first two centuries of the Roman Empire, especially regarding the transition from Republic to Principate.
Σοῦδα Δίων ὁ Κάσσιος χρηματίσας .... ἔγραψε Ῥωμαικὴν ἱστορίαν ἐν βιβλίοις π — διαιροῦνται δὲ κατὰ δεκάδας· Περσικά Γετικά· Ἐνόδια· Τὰ κατὰ Τραιανόν· Βίον Ἀρριανοῦ τοῦ φιλοσόφου.
Φιλόστρατος ὁ Ἀθηναῖος ὡς δὲ καὶ ἱστορίαν ἱκανὸς ἦν ξυγγράφειν δηλοῖ τὰ Γετικά· καὶ γὰρ δὴ καὶ ἐς Γέτας ἦλθεν, ὁπότε ἠλᾶτο.
Δίων ὁ Χρυσόστομος ἐτύγχανον μὲν ἐπιδημῶν ἐν Βορυσθένει τὸ θέρος, ὁπότε εἰσέπλευσα μετὰ τὴν φυγήν, βουλόμενος ἐλθεῖν, ἐὰν δύνωμαι, διὰ Σκυθῶν εἰς Γέτας, ὅπως θεάσωμαι τἀκεῖ πράγματα ὁποῖά ἐστι κτλ.
